Measurement of out-of-plane thermal conductivity of substrates for flexible electronics and displays

Vishwakarma, Vivek; Waghela, Chirag; Jain, Ankur

doi:10.1016/j.mee.2015.06.008

Cited by 13 publications

(6 citation statements)

References 24 publications

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“…The inlaid insulation however leads to a parasitic heat flow bypassing the thermoelectric material and an overall reduction of the power conversion efficiency. For the devices fabricated in this work a quick estimation with the dimension given in the layout, the thermal conductivities from Table 1, and the thermal conductivity of PEN 34 of 0.22 Wm −1 K −1 yields that the thermal resistance of the origami TEGs is 24.53% lower than if the TE elements were separated by 6 μm of air 35 with the thermal conductivity of 0.0264 Wm −1 K −1 . This effect is thereby rather significant.…”

Section: Fabrication Of Origami Folded Devicesmentioning

confidence: 99%

Fully printed origami thermoelectric generators for energy-harvesting

et al. 2021

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Energy-harvesting from low-temperature environmental heat via thermoelectric generators (TEG) is a versatile and maintenance-free solution for large-scale waste heat recovery and supplying renewable energy to a growing number of devices in the Internet of Things (IoT) that require an independent wireless power supply. A prerequisite for market competitiveness, however, is the cost-effective and scalable manufacturing of these TEGs. Our approach is to print the devices using printable thermoelectric polymers and composite materials. We present a mass-producible potentially low-cost fully screen printed flexible origami TEG. Through a unique two-step folding technique, we produce a mechanically stable 3D cuboidal device from a 2D layout printed on a thin flexible substrate using thermoelectric inks based on PEDOT nanowires and a TiS2:Hexylamine-complex material. We realize a device architecture with a high thermocouple density of 190 per cm² by using the thin substrate as electrical insulation between the thermoelectric elements resulting in a high-power output of 47.8 µWcm−² from a 30 K temperature difference. The device properties are adjustable via the print layout, specifically, the thermal impedance of the TEGs can be tuned over several orders of magnitudes allowing thermal impedance matching to any given heat source. We demonstrate a wireless energy-harvesting application by powering an autonomous weather sensor comprising a Bluetooth module and a power management system.

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Section: Fabrication Of Origami Folded Devicesmentioning

confidence: 99%

Fully printed origami thermoelectric generators for energy-harvesting

et al. 2021

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“…However, these very thin and flexible substrates tend to have thermal conductivity issues when they are used for applications with high power dissipating profiles. The low thickness and low thermal conductivity of these substrate materials can cause poor heat spreading performance while, factors such as excessive thermal expansion and low glass transition temperature can change the physical and chemical properties of the substrate materials under the heat [ 13 ].…”

Section: Printing Electronics For a Lower Environmental Impactmentioning

confidence: 99%

Light-Based IoT: Developing a Full-Duplex Energy Autonomous IoT Node Using Printed Electronics Technology

Perera

Katz

Häkkinen

et al. 2021

Sensors

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The light-based Internet of things (LIoT) concept defines nodes that exploit light to (a) power up their operation by harvesting light energy and (b) provide full-duplex wireless connectivity. In this paper, we explore the LIoT concept by designing, implementing, and evaluating the communication and energy harvesting performance of a LIoT node. The use of components based on printed electronics (PE) technology is adopted in the implementation, supporting the vision of future fully printed LIoT nodes. In fact, we envision that as PE technology develops, energy-autonomous LIoT nodes will be entirely printed, resulting in cost-efficient, flexible and highly sustainable connectivity solutions that can be attached to the surface of virtually any object. However, the use of PE technology poses additional challenges to the task, as the performance of these components is typically considerably poorer than that of conventional components. In the study, printed photovoltaic cells, printed OLEDs (organic light-emitting diodes) as well as printed displays are used in the node implementation. The dual-mode operation of the proposed LIoT node is demonstrated, and its communication performance in downlink and uplink directions is evaluated. In addition, the energy harvesting system’s behaviour is studied and evaluated under different illumination scenarios and based on the results, a novel self-operating limitation aware algorithm for LIoT nodes is proposed.

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“…Total thermal resistance across a material stack is determined by sandwiching the stack between two identical copper blocks [28]. Fig.…”

Section: Thermal Measurementsmentioning

confidence: 99%

Heat transfer enhancement in a lithium-ion cell through improved material-level thermal transport

Vishwakarma

Waghela

et al. 2015

Journal of Power Sources

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h i g h l i g h t sIdentifies rate-limiting material-level thermal conduction process in a Li-ion cell. Shows that interfacial thermal conduction between cathode and separator contributes 88% of total thermal resistance. Experimental data agrees with theoretical model on thermal contact resistance. Chemical bridging of this interface results in 4X reduction in thermal contact resistance. Results may contribute towards thermal safety of Li-ion cells. a b s t r a c tWhile Li-ion cells offer excellent electrochemical performance for several applications including electric vehicles, they also exhibit poor thermal transport characteristics, resulting in reduced performance, overheating and thermal runaway. Inadequate heat removal from Li-ion cells originates from poor thermal conductivity within the cell. This paper identifies the rate-limiting material-level process that dominates overall thermal conduction in a Li-ion cell. Results indicate that thermal characteristics of a Liion cell are largely dominated by heat transfer across the cathode-separator interface rather than heat transfer through the materials themselves. This interfacial thermal resistance contributes around 88% of total thermal resistance in the cell. Measured value of interfacial resistance is close to that obtained from theoretical models that account for weak adhesion and large acoustic mismatch between cathode and separator. Further, to address this problem, an amine-based chemical bridging of the interface is carried out. This is shown to result in in four-times lower interfacial thermal resistance without deterioration in electrochemical performance, thereby increasing effective thermal conductivity by three-fold. This improvement is expected to reduce peak temperature rise during operation by 60%. By identifying and addressing the material-level root cause of poor thermal transport in Li-ion cells, this work may contributes towards improved thermal performance of Li-ion cells.

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Measurement of out-of-plane thermal conductivity of substrates for flexible electronics and displays

Cited by 13 publications

References 24 publications

Fully printed origami thermoelectric generators for energy-harvesting

Fully printed origami thermoelectric generators for energy-harvesting

Light-Based IoT: Developing a Full-Duplex Energy Autonomous IoT Node Using Printed Electronics Technology

Heat transfer enhancement in a lithium-ion cell through improved material-level thermal transport

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